1. Field of the Invention
The present invention relates to a liquid container that is used, for example, as an ink tank mounted on an inkjet recording apparatus and is brought into contact with an external member for supplying liquid thereto. The present invention also relates to a liquid ejecting cartridge that ejects liquid.
2. Description of the Related Art
In a known inkjet recording apparatus that performs recording by ejecting ink droplets, an inkjet head and an ink tank, which are separate, are brought together when the inkjet recording apparatus is used. To stably retain and supply ink during a recording operation to an inkjet head, an ink tank for such an inkjet recording apparatus needs to have a mechanism for generating appropriate back pressure (negative pressure). A known method for generating negative pressure utilizes a porous member, such as a urethane foam body, as a negative pressure generating member (ink absorber) to use the capillary force of the porous member.
Generally, the capillary force of a nozzle, according to the amount of ink consumed by an ejecting part, allows ink held by the porous member to flow from an ink supply port of the ink tank via a common reservoir to the ejecting part. Japanese Patent Laid-Open No. 7-148937 (corresponding U.S. Pat. No. 5,619,239) discloses a structure in which ribs for preventing ink leakage are provided in an ink tank.
An exemplary known ink tank using the capillary force will be described with reference to FIG. 8, FIG. 9A, and FIG. 9B.
FIG. 8 is an external perspective view of an ink tank and FIGS. 9A and 9B are cross-sectional views of the ink tank. FIG. 9A is a cross-sectional view taken along line IXA-IXA of FIG. 8, and FIG. 9B is a cross-sectional view taken along line IXB-IXB of FIG. 8. For the ease of explanation, the drawings show an ink tank 100 separated from a holder.
As shown in FIG. 8 and FIG. 9A, the ink tank 100 includes a housing constituting an ink container. The housing includes a main body 111a with an opening at the top and a lid member 111b for covering the opening of the main body 111a. The lid member 111b is provided with an air hole 115 for allowing air into the housing, and lid ribs 113 for allowing a space for buffering. The bottom of the main body 111a of the housing is provided with an ink supply port 114 for supplying ink to an inkjet head (not shown).
The housing contains a first ink retainer 150 and a second ink retainer 151 that are impregnated with and retain ink. The first ink retainer 150 is disposed between the second ink retainer 151 and the bottom of the ink tank 100. An end face of the first ink retainer 150 is in intimate contact with the second ink retainer 151 and blocks the ink supply port 114 from inside the housing.
As shown in FIG. 9A and FIG. 9B, the inner wall of the main body 111a is provided with a plurality of side ribs 112 surrounding the second ink retainer 151. The second ink retainer 151 contained in the housing is pressed against the side ribs 112 and creates clearances around the side ribs 112. The clearances are not filled with the second ink retainer 151 and communicate with the air hole 115.
The ink supply port 114 of the ink tank 100 is provided with a cap 117 for preventing ink leakage and evaporation during product distribution.
Although the first ink retainer 150 and the second ink retainer 151 are both impregnated with and retain ink, the ink retaining force (capillary force) of the first ink retainer 150 is larger than that of the second ink retainer 151. This enables ink retained by the second ink retainer 151 to smoothly flow into the first ink retainer 150 and increases efficiency of the consumption of the ink retained by the second ink retainer 151.
A mechanism based on the above-described structure for preventing ink leakage will now be described with reference to FIGS. 10A to 10C and FIGS. 11A to 11C.
FIGS. 10A to 10C and FIGS. 11A to 11C are cross-sectional views showing ink tanks capped for product distribution. In each ink tank, an air hole serving as an opening for allowing air into the ink tank faces downward. FIGS. 10A to 10C are cross-sectional views of an ink tank with no rib thereinside. FIGS. 11A to 11C are cross-sectional views of an ink tank with ribs thereinside.
First, an ink tank with no rib thereinside will be described with reference to FIGS. 10A to 10C.
When shock is applied to the ink tank 100 downward in the drawings (toward a surface on which the air hole 115 is provided) during product handling or the like, ink 119 retained near the ink supply port 114 in the ink retainers is moved toward the air hole 115. Since the ink retaining force of the first ink retainer 150 is larger than that of the second ink retainer 151, the ink 119 in the first ink retainer 150 is not easily moved by the application of the shock. Therefore, the ink 119 mainly in the second ink retainer 151 is moved toward the air hole 115.
As shown in FIG. 10B, voids 120 in which no ink 119 is retained are created, as the ink 119 moves, near the boundary between the first ink retainer 150 and the second ink retainer 151. When temperature or barometric pressure changes under this condition, the expansion of air in the voids 120, which are closed spaces surrounded by the ink 119, pushes the ink 119 in the second ink retainer 151 in directions indicated by arrows in FIG. 10C, and eventually causes the ink 119 to leak from the air hole 115 of the ink tank 100.
Next, an ink tank with ribs thereinside will be described with reference to FIGS. 11A to 11C.
When shock is applied to the ink tank 100 downward in the drawings (toward the surface on which the air hole 115 is provided) during product handling or the like, the voids 120 in which no ink 119 is retained are created, as the ink 119 moves, in the boundary between the first ink retainer 150 and the second ink retainer 151, as shown in FIG. 11B similar to those shown in FIG. 10B. When temperature or barometric pressure in the ink tank 100 with ribs thereinside changes, the voids 120 quickly communicate with clearances around the side ribs 112 and further communicate with the air hole 115. Therefore, as shown in FIG. 11C, air flows through air paths 123 indicated by broken lines and pushes almost no ink 119 outward.
As inkjet recording apparatuses become widespread, compact recording apparatuses with excellent portability have been developed. In such a compact recording apparatus, the size of its ink tank as well as the size of its main body is small.
Japanese Patent Laid-Open No. 2004-230702 (corresponding U.S. Pat. No. 6,942,326) discloses a structure that increases the efficiency of the use of space in a known compact ink tank and allows stable supply operations of the ink tank.
The structure will now be described with reference to FIG. 12 and FIG. 13. FIG. 12 is an exploded perspective view showing an external appearance of a known ink tank and inkjet head with holder before being put together, and FIG. 13 is an exploded partial cutaway perspective view of FIG. 12.
As shown in FIG. 12 and FIG. 13, an inkjet cartridge 130 includes an ink tank 100, a holder 131 detachably holding the ink tank 100, and an inkjet head 132 that is integral with the holder 131 and ejects ink.
The inkjet head 132 is provided at the bottom of the holder 131 in use mode during which ink is ejected, and has a group of outlets (not shown) for ejecting ink supplied from the ink tank 100. The holder 131 is provided with a projecting ink receiving tube (external member) 133 at a connection to the ink tank 100. The ink receiving tube 133 communicates via an ink supply path (not shown) with the group of outlets of the inkjet head 132.
As shown in FIG. 12, the ink tank 100 includes a housing 111 constituting an ink container. The housing 111 includes a main body 111a with an opening at the top and a lid member 111b for covering the opening of the main body 111a. The lid member 111b is provided with an air hole 115 and lid ribs 113 for allowing space for buffering.
As shown in FIG. 13, the bottom of the main body 111a of the housing 111 is provided with an ink supply port 114 that is opposite the ink receiving tube 133 when the ink tank 100 is attached to the holder 131. The housing 111 contains a first ink retainer 150 and a second ink retainer 151 that are impregnated with and retain ink.
The first ink retainer 150 is disposed between the second ink retainer 151 and the bottom of the ink tank 100. The first ink retainer 150 is in intimate contact with the second ink retainer 151 and blocks the ink supply port 114 from inside the ink tank 100. The first ink retainer 150 is formed substantially into the inner shape of a portion (undersurface) of the housing 111, the portion in which the ink supply port 114 is provided. The ink retaining force (capillary force) of the first ink retainer 150 is larger than that of the second ink retainer 151.
Since the first ink retainer 150 is formed substantially into the inner shape of the undersurface of the housing 111 in the structure described above, an area impregnated with ink increases inside the ink tank 100. This allows a relatively large amount of ink to be retained in a small ink tank. Moreover, even if ink is supplied at high speed, the amount of unused ink remaining in the ink tank 100 can be reduced and the efficiency of ink use can be increased.
If the first ink retainer 150 is in sheet form, a local deformation that occurs when brought into contact with an external member can be accommodated by the first ink retainer 150 as a whole, and neighboring voids generated by the buckling of the first ink retainer 150 can be minimized. Moreover, reducing the internal volume of the first ink retainer 150 having a relatively large capillary force can reduce the amount of ink remaining inside the first ink retainer 150 and increase the efficiency of ink use.
As inkjet recording apparatuses become widespread, compact recording apparatuses with excellent portability have been proposed these days. In such a compact recording apparatus, the size of its ink tank as well as the size of its main body is small. An important point for such a compact ink tank is how to avoid ink leakage without reducing the efficiency of space use.
However, in a known structure, many ribs for avoiding ink leakage are provided on the inner surface of a housing of an ink tank and create space between an ink retainer and the inner surface of the housing. Therefore, the amount of space in which the ink retainer retains ink is reduced by the amount of space created by the ribs.
As disclosed in the above-described Japanese Patent Laid-Open No. 2004-230702 (corresponding U.S. Pat. No. 6,942,326), in the ink tank 100 in which the first ink retainer 150 is disposed over the entire undersurface of the housing 111 to increase the efficiency of ink use, a large enclosed air space is created between the first ink retainer 150 and the second ink retainer 151 because of the large area of the first ink retainer 150, and the possibility of ink leakage increases. However, if more ribs are added to increase resistance to ink leakage, the amount of space in which ink is retained is further reduced.